Seahenge, Norfolk

In 1998, a man walking his dog on the beach at Holme-next-the-Sea stumbled on a circle of tree trunks buried in the sand. The mysterious bronze age monument was uncovered and the 4,000-year-old timbers were carted off for conservation. Channel 4's Time Team constructed a full-size replica a few miles inland in Thornham. The original is in the Lynn Museum, Kings Lynn.• Drove Farm orchard; 01485 525 652. Lynn Museum, Market Street; 01553 775 001 Dave Newnham

Boscawen-un, Cornwall

Hidden in thick gorse is one of the finest prehistoric sites in Cornwall, 19 upright granite blocks placed around a leaning stone, just south of the centre. • Near to St BuryanOS map ref: SW412274 Chris Collyer

Navan Fort, Armagh

Seat of King Conchobar and one of the most important prehistoric sites in Northern Ireland. Excavations revealed curiously shaped wooden buildings beneath the barrow and mound which had been deliberately burned Near Armagh City. • OS map ref: H847452 CC